1. Field of the Invention
The invention generally relates to methods and apparatus for connecting instrumentation lines in a wellbore. More particularly, the invention provides methods and apparatus for delivering a fiber optic cable to a selected depth within a hydrocarbon wellbore.
2. Description of the Related Art
In a typical oil or gas well, a borehole drilled into the surface of the earth extends downward into a formation to provide a wellbore. The wellbore may include any number of tubular strings such as a string of surface casing cemented into place and a liner string hung off of the casing that extends into a producing zone, or pay zone, where the liner is perforated to permit inflow of hydrocarbons into the bore of the liner. Alternatively, the wellbore may be completed as an open hole which may include a sand screen positioned at the end of the casing to support the formation and filter hydrocarbons that pass therethrough. During the life of the well, it is sometimes desirable to monitor conditions in situ. Recently, technology has enabled well operators to monitor conditions within a wellbore by installing permanent monitoring systems downhole. The monitoring systems permit the operator to monitor such parameters as multiphase fluid flow, as well as pressure and temperature. Downhole measurements of pressure, temperature and fluid flow play an important role in managing oil and gas or other sub-surface reservoirs.
Historically, permanent monitoring systems have used electronic components to provide pressure, temperature, flow rate and water fraction data on a real-time basis. These monitoring systems employ temperature gauges, pressure gauges, acoustic sensors, and other instruments, or “sondes,” disposed within the wellbore. Such electrical instruments are either battery operated, or are powered by electrical cables deployed from the surface. Typically, conductive electrical cables transmit the electrical signals from the electronic sensors back to the surface.
Recently, optical sensors have been developed which communicate readings from the wellbore to optical signal processing equipment located at the surface. The optical sensors may be variably located within the wellbore and do not require an electrical line from the surface. For example, optical sensors may be positioned in fluid communication with the housing of a submersible electrical pump. Such an arrangement is taught in U.S. Pat. No. 5,892,860, issued to Maron, et al., in 1999. The '860 patent is incorporated herein in its entirety, by reference. Optical sensors may also be disposed along the tubing within a wellbore to sense the desired parameters. As another example of an optical sensor, a distributed temperature sensor system is a known measurement technique that provides a continuous temperature profile along the entire length of an optical fiber. Distributed temperature sensor systems operate on the principle of backscattering, the known velocity of light and the thermal energy in the optical fiber. Regardless of the type of optical sensor, an optical waveguide or fiber optic cable runs from the surface to the optical sensor downhole. Surface equipment transmits optical signals to the downhole optical sensors via the fiber optic cables which transmit return optical signals to an optical signal processor at the surface.
Therefore, both optical and electronic sensors often require an instrumentation line such as a fiber optic cable, a wire or a conductive electric cable that runs down the wellbore to the sensor. The instrumentation line may run down the outer surface of one of the tubular strings in the wellbore such as production tubing and clamp thereto at intervals as is known in the art. When the instrumentation line is on the outside of a liner or sand screen, the instrumentation line may be subjected to trauma or damage as the liner or sand screen runs into the wellbore. Trauma further increases where the instrumentation line is disposed along the outer surface of an expanded liner or sand screen since the instrumentation line compresses between the outer surface of the liner or sand screen and the surrounding formation.
Further, the instrumentation line may be exposed to the harsh effects of chemicals used in well completion or remediation operations. For example, it is oftentimes desirable to wash the tubing in order to remove grease and contaminants during a last stage in well completion. This is accomplished by circulating acid through the tubing. In addition, an acid wash or other stimulant may clean the sand screen and tubing of paraffins, hydrates and scale that accumulate along the sand screen and tubing during the life of a producing well. The application of such chemicals may be detrimental to the integrity of the instrumentation line. This is particularly true where the instrumentation line is a fiber optic cable of a distributed temperature sensor system. A packer may isolate an upper section of the instrumentation line from the chemicals used in the well completion or remediation operations such that only a lower section of the instrumentation line is subject to the harsh chemicals.
The expandable sand screen may include protective features that help protect the instrumentation line disposed along the outside of the sand screen as the sand screen is run and expanded. For example, the instrumentation line may pass along a recess in the outer diameter of the sand screen. Arrangements for the recess are described more fully in the application entitled “Profiled Recess for Instrumented Expandable Components,” having Ser. No. 09/964,034, now U.S. Pat. No. 6,877,553 issued Apr. 12. 2005. which is incorporated herein in its entirety, by reference. Alternatively, a specially profiled encapsulation around the sand screen which contains arcuate walls may house the instrumentation line. Arrangements for the encapsulation are described more fully in the application entitled “Profiled Encapsulation for Use with Expandable Sand Screen,” having Ser. No. 09/964,160, now U.S. Pat. No. 6,932,161 issued Aug. 23, 2005, which is also incorporated herein in its entirety, by reference. However, these protective features fail to protect the instrumentation line from the chemicals used during well completion and remediation operations. With the instrumentation line clamped to a liner or sand screen and/or disposed in a protective feature of a sand screen, it is not possible to pull the instrumentation line during an acid wash or other remedial operation, at least not without pulling the tubular and/or sand screen.
Therefore, there exists a need for a method of installing an instrumentation line into a wellbore after expansion of a sand screen or other liner, after setting of a packer, and/or after conducting an acid wash. Further, a need exists for a coupling apparatus that permits a lower instrumentation line to connect downhole with an upper instrumentation line after the upper instrumentation line is placed in the wellbore. There exists a further need for a coupling apparatus that allows the lower instrumentation line to be detached and removed from the wellbore without removing the upper instrumentation line.